This application is based on an application No. 11-305809 filed in Japan, the content of which is hereby incorporated by reference.
(1) Field of the Invention
The present invention relates to a fuel cell generator that electrolyzes water to generate hydrogen and generates electricity using the hydrogen.
(2) Related Art
The fuel cell generator supplies hydrogen-rich gas to the anode of the fuel cell, oxidizer gas to the cathode, electrochemically reacts hydrogen and oxidizer to generate electricity. As described in Japanese Patent Laid-Open Publication No. Hei 10-233225, leveling off the load on the utility power system using the fuel cell generator has been recently under study.
FIG. 9 is a functional diagram of an example of the fuel cell generator.
In FIG. 9, the fuel cell generator includes a fuel cell 201, an electricity converter 202, a fuel gas supplying system 203, an oxidizer gas supplying system 204, an electrolytic device 211, a hydrogen storage device 212. The electricity converter 202 converts direct current power from the fuel cell 201 into alternating current power. The fuel gas supplying system 203 and the oxidizer gas supplying system 204 supply fuel gas and oxidizer gas to the fuel cell 201, respectively. The electrolytic device 211 electrolyzes water. The hydrogen storage device 212 stores the hydrogen generated by the electrolytic device 211. The electricity converter 202 is connected to a utility power system 210 via a switch 221, and the electrolytic device 211 is connected via a switch 222.
In this fuel cell generator in FIG. 9, the switch 222 is turned on to provide utility power to the electrolytic device 211 during the night when electricity charge is inexpensive. In this case, water is electrolyzed in the electrolytic device 211 to generate hydrogen. The generated hydrogen is stored in the hydrogen storage device 212.
On the other hand, hydrogen stored in the hydrogen storage device 212 is supplied to the anode of the fuel cell 201 via the fuel gas supplying system 203, air is supplied to the cathode via the oxidizer gas supplying system 204, and electricity is.generated in the fuel cell 201 during the daytime when the power consumption is at its peak. In this case, the direct current power generated in the fuel cell 201 is converted into alternating current power and to be supplied to the utility power system 210 via the switch 221.
In this manner, hydrogen is generated using inexpensive electricity during the night, and electricity is generated using the hydrogen during the daytime to supply the generated power to the utility power system. By doing so, the power load on the utility power system can be leveled off.
It is accordingly the object of the present invention to improve the system efficiency of the fuel cell generator.
The above-mentioned object may be achieved by a fuel cell generator including: a fuel cell that generates electricity using hydrogen; an electrolytic device that electrolyzes water using electricity from an external electricity system; a hydrogen storage device that (A) stores hydrogen that has been generated in the electrolytic device during the electrolysis and (B) supplies the stored hydrogen to the fuel cell; and an heat supplying device that supplies heat that has been generated in the fuel cell during the electricity generation to the electrolytic device.
In the fuel cell generator, it is preferable to provide the heat supplying device with a heat storage unit for storing heat and to supply heat to the electrolytic device during the operation of the electrolytic device so that the heat that has been generated during the operation of the fuel cell is used by the electrolytic device. For this purpose, it is also preferable to design an electrolytic cell of the electrolytic device to keep warm.
By doing so, the heat generated during the electricity generation by the fuel cell is used for heating the electrolytic device and less amount of electricity is consumed for the electrolysis. As a result, the system efficiency is improved compared with the conventional fuel cell generator.
This can be explained as follows. Water electrolysis is an endothermic reaction, so that heat needs to be supplied to the water that is to be electrolyzed in the electrolytic device. For this reason, the higher the temperature of the water that is electrolyzed, the less the amount of energy that is consumed in the electrolytic device.
Also, the fuel cell generator of this kind is mainly operated during the night when the environmental temperature is low. Accordingly, the temperature of the electrolytic device is also low, so that a large amount of electricity tends to be consumed for the electrolysis. In the fuel cell generator of the present invention, however, the heat that has been generated in the fuel cell during the electricity generation is used for the electrolysis. As a result, the amount of electricity consumed by the electrolytic device can be drastically reduced.
The above-mentioned object may be also achieved by a fuel cell generator including a fuel cell that has a function to generate electricity using hydrogen and another function to electrolyze water using electricity from an external electricity system. In this case, the same function as the fuel cell generator that has been described above can be realized without disposing an electrolytic device. As a result, the facility cost can be reduced.